fix 202 bugs (#418)

* fix peer rpc stop working because of mpsc tunnel close unexpectedly

* fix gui:

1. allow set network prefix for virtual ipv4
2. fix android crash
3. fix subnet proxy cannot be set on android

easytier-gui/src/composables/mobile_vpn.ts

@@ -48,7 +48,7 @@ async function doStartVpn(ipv4Addr: string, cidr: number, routes: string[]) {
 
   console.log('start vpn')
   const start_ret = await start_vpn({
-    ipv4Addr: `${ipv4Addr}/${cidr}`,
+    ipv4Addr: `${ipv4Addr}`,
     routes,
     disallowedApplications: ['com.kkrainbow.easytier'],
     mtu: 1300,